Office chairs have been developed which permit the back assembly to be tilted synchronously with the seat assembly but at a greater rate so that the back assembly tilts relative to the seat assembly as the latter tilts relative to the chair base. Such chairs also effectively permit tilting of the seat about an axis located adjacent the front edge thereof so as to prevent undesired lifting of the seat front edge when the occupant tilts the chair rearwardly. Nevertheless, most of the known chairs have accomplished these objectives only by use of complex structures and functional relationships which have required an undesirably large number of parts and have accordingly increased the overall complexity of assembling the chair. Such chairs hence have been more costly than desired.
Accordingly, it is an object of this invention to provide an improved chair which provides for synchronous differential tilting of the seat and back assemblies, with the seat assembly being constructed such that the front lip thereof does not significantly raise or lift upwardly upon rearward tilting, which improved chair is of simplified construction and assembly so as to overcome disadvantages of the type associated with prior chairs of this general type.
More specifically, according to one aspect of the invention, the improved chair, as aforesaid, incorporates a tilt control mechanism formed by a control body which secures to the upper end of the chair pedestal and an upright which pivotally connects to the control body about an axis disposed forwardly of the pedestal, with an improved pivot assembly being provided for connecting the upright and control body together, which pivot assembly is of improved structural simplicity and provides simplified assembly.
A further aspect of the invention is an improved chair, as aforesaid, which incorporates a one-piece molded chair shell which mounts to the control mechanism and defines both the seat and back of the chair, with the shell being secured to the control mechanism totally by substantially snap-fit latches and cooperating stops which are formed directly on and coact directly between the shell and the control mechanism, whereby the securement of the shell to the control mechanism is free of separate fasteners, thereby simplifying the overall assembly of the shell to the control mechanism.
A still further aspect of the invention is an improved chair having side arms which connect between the seat and back adjacent opposite sides of the chair, the arms at their lower front ends having hub portions which are structurally supported on outwardly projecting cantilevered ends of a main support or pivot shaft, with the chair arms being fixedly locked to an internal seat structure by a relatively-rotatable cam locking arrangement so that assembly of the front ends of the arms to the seat assembly is greatly simplified.
Another aspect of the invention is an improved chair, as aforesaid, having an improved tilt lock mechanism which cooperates between the control body and the upright so as to permit the chair to be locked either in a normal upright position or in a rearwardly tilted position, which tilt lock mechanism is of relatively simple and inexpensive construction, and is disposed within a minimal space as provided rearwardly of the control body.
Still another aspect of the invention is an improved chair having an airlift cylinder associated with the pedestal for adjusting the height of the seat assembly, and particularly an improved release mechanism for controlling activation of the airlift cylinder, which release mechanism is of structural simplicity in terms of minimal number of parts so as to reduce assembly time and cost, and which mechanism additionally permits activation of the airlift cylinder in response to an activating lever being manually displaced either upwardly or downwardly from its normal locked position.
Other objects and purposes will be apparent to persons familiar with structures similar to the present invention upon reading the following specification and inspecting the accompanying drawings.